Many structures, such as silos, factories, houses and shipping containers are subjected to fumigation. Fumigants such as methyl bromide, however, are highly toxic and may damage the health of those exposed to the gas. Methyl bromide damages the ozone layer if released into the atmosphere. A fumigant, typically in the form of a gas, is ideally introduced into the structure while maintaining a seal against the leakage of the fumigant at the point the fumigant is introduced.
Toxic gases may build up inside a structure. For example, the contents of a shipping container (especially freight containers, otherwise known as intermodal containers) may release toxic gases. The toxic gas may originate from a constituent of the contents (such as a varnish finish). Alternatively, the toxic gas may be a fumigant absorbed or adsorbed during fumigation of the container's contents, typically at the port from which the container departed, and then released during the shipping period. It is desirable to remove any residual gases, such as toxic gases, from the container before a person enters it or even, in some circumstances, substantially opened.